1 //===- MCSectionCOFF.h - COFF Machine Code Sections -------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file declares the MCSectionCOFF class. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #ifndef LLVM_MC_MCSECTIONCOFF_H 14 #define LLVM_MC_MCSECTIONCOFF_H 15 16 #include "llvm/ADT/StringRef.h" 17 #include "llvm/BinaryFormat/COFF.h" 18 #include "llvm/MC/MCSection.h" 19 #include "llvm/MC/SectionKind.h" 20 #include <cassert> 21 22 namespace llvm { 23 24 class MCSymbol; 25 26 /// This represents a section on Windows 27 class MCSectionCOFF final : public MCSection { 28 // FIXME: The following fields should not be mutable, but are for now so the 29 // asm parser can honor the .linkonce directive. 30 31 /// This is the Characteristics field of a section, drawn from the enums 32 /// below. 33 mutable unsigned Characteristics; 34 35 /// The unique IDs used with the .pdata and .xdata sections created internally 36 /// by the assembler. This ID is used to ensure that for every .text section, 37 /// there is exactly one .pdata and one .xdata section, which is required by 38 /// the Microsoft incremental linker. This data is mutable because this ID is 39 /// not notionally part of the section. 40 mutable unsigned WinCFISectionID = ~0U; 41 42 /// The COMDAT symbol of this section. Only valid if this is a COMDAT section. 43 /// Two COMDAT sections are merged if they have the same COMDAT symbol. 44 MCSymbol *COMDATSymbol; 45 46 /// This is the Selection field for the section symbol, if it is a COMDAT 47 /// section (Characteristics & IMAGE_SCN_LNK_COMDAT) != 0 48 mutable int Selection; 49 50 unsigned UniqueID; 51 52 private: 53 friend class MCContext; 54 // The storage of Name is owned by MCContext's COFFUniquingMap. MCSectionCOFF(StringRef Name,unsigned Characteristics,MCSymbol * COMDATSymbol,int Selection,unsigned UniqueID,MCSymbol * Begin)55 MCSectionCOFF(StringRef Name, unsigned Characteristics, 56 MCSymbol *COMDATSymbol, int Selection, unsigned UniqueID, 57 MCSymbol *Begin) 58 : MCSection(SV_COFF, Name, Characteristics & COFF::IMAGE_SCN_CNT_CODE, 59 Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA, 60 Begin), 61 Characteristics(Characteristics), COMDATSymbol(COMDATSymbol), 62 Selection(Selection), UniqueID(UniqueID) { 63 assert((Characteristics & 0x00F00000) == 0 && 64 "alignment must not be set upon section creation"); 65 } 66 67 public: 68 /// Decides whether a '.section' directive should be printed before the 69 /// section name 70 bool shouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const; 71 getCharacteristics()72 unsigned getCharacteristics() const { return Characteristics; } getCOMDATSymbol()73 MCSymbol *getCOMDATSymbol() const { return COMDATSymbol; } getSelection()74 int getSelection() const { return Selection; } 75 76 void setSelection(int Selection) const; 77 isUnique()78 bool isUnique() const { return UniqueID != NonUniqueID; } getUniqueID()79 unsigned getUniqueID() const { return UniqueID; } 80 81 void printSwitchToSection(const MCAsmInfo &MAI, const Triple &T, 82 raw_ostream &OS, 83 uint32_t Subsection) const override; 84 bool useCodeAlign() const override; 85 StringRef getVirtualSectionKind() const override; 86 getOrAssignWinCFISectionID(unsigned * NextID)87 unsigned getOrAssignWinCFISectionID(unsigned *NextID) const { 88 if (WinCFISectionID == ~0U) 89 WinCFISectionID = (*NextID)++; 90 return WinCFISectionID; 91 } 92 isImplicitlyDiscardable(StringRef Name)93 static bool isImplicitlyDiscardable(StringRef Name) { 94 return Name.starts_with(".debug"); 95 } 96 classof(const MCSection * S)97 static bool classof(const MCSection *S) { return S->getVariant() == SV_COFF; } 98 }; 99 100 } // end namespace llvm 101 102 #endif // LLVM_MC_MCSECTIONCOFF_H 103